JP5106534B2 - Cryostat and access turret / refrigerator turret subassembly used as part thereof and method of assembling the cryostat - Google Patents

Description

The present invention relates to a cryostat container for holding a cooled device such as a superconducting magnet coil. In particular, the invention provides an access device for a cryostat vessel that allows a current lead to enter the cryostat vessel to supply current to the cooled device; and allows cryogenic refrigerant gas to escape from the cryostat; A venting device that provides access to refill the cryogenic refrigerant when needed; and a turret device for holding the refrigerator in thermal contact with the cryogenic refrigerant .

FIG. 1 shows a conventional apparatus comprising an access turret, a vent pipe, a current lead, and a refrigerator in a cryostat. The superconducting magnet 10 to be cooled is provided in a cryogenic refrigerant container 12 itself held in an outer vacuum chamber (OVC) 14. One or more thermal radiation shields 16 may be provided in the vacuum space between the cryogenic refrigerant container and the outer vacuum chamber. Although it is known that the refrigerator 17 is placed in a turret 18 provided towards the side of the cryostat for this purpose, the conventional device has an access neck (vent pipe) 20 attached to the top of the cryostat. Has an access turret 19.

The magnet 10 is usually provided with a negative current lead 21a through the body of the cryostat. The positive current lead 21 is typically provided by a conductor that passes through the vent tube 20.

  For a fixed current lead (FCL) design, another vent path (auxiliary vent) (not shown in FIG. 1) is provided as a failsafe vent when the vent tube is clogged.

The present invention aims to overcome, or at least reduce, many of the identified disadvantages of conventional designs. The present invention aims to allow an access turret combined with a refrigerator turret to be moved from the top to the side of the system. This results in a reduction in overall system height, as described below, and provides the benefits of ease of manufacture and reduced scrap. The conventional separation of access turret and refrigerator turret means that the cryogenic refrigerant container must be provided with two separate access ports (holes). The present invention aims to reduce this to a single access port. This simplifies the assembly of the cryogen vessel, also reduce the heat influx to the cryogenic refrigerant container by reducing the number of thermal paths to cryogen vessel. Each port needs to be sealed during final assembly of the cryostat by welding to an appropriate turret. Such welding to thin-walled components is difficult to achieve and causes some manufacturing difficulties and rework and scrap. The present invention also aims to eliminate the need for welding to a thin turret during final assembly of the cryostat.

Conventionally, current leads have been applied to the superconducting magnet in the cryostat as follows.
Referring briefly to FIG. 4, one connection is made through the body of the cryogenic refrigerant container 12, typically a negative current lead 21a. This is typically done by bolting or soldering a flexible current lead to the base of the vent tube 20. Other current leads 21 have been made by energizing through a conductive auxiliary vent 40 located in the access neck 20. The flexible positive current lead 21 is typically soldered or bolted to the auxiliary vent 40 during final assembly of the cryostat to electrically connect the auxiliary vent to the magnet. The auxiliary vent 40 is typically arranged to be cooled by allowing the cryogenic refrigerant gas to escape and is not shown at least by a burst disk not shown but well known to those skilled in the relevant art. Sealed to some extent.

The disadvantage of the conventional termination configuration is that the contact resistance at the junction between the flexible current leads 21, 21 a, the vent pipe 20 and the auxiliary vent 40 dissipates heat at the base of the vent pipe 20 in the cryogenic refrigerant container 12. It is to let you. This raises the temperature of the nearby cryogenic refrigerant gas during ramping through conduction and convection of the cryogenic refrigerant gas in the cryogenic refrigerant container. Typically, existing systems are intended to operate at a cryogenic refrigerant container gas temperature of about 5K for a typical cryogenic refrigerant consisting of liquid helium. Variations in contact resistance at the point where the flexible current leads 21, 21a from the magnet are connected to the vent tube 20 and the auxiliary vent 40 can cause power dissipation during ramping and much more than intended in some systems. Cause high cryogenic refrigerant gas temperature. This is known to result in excessive quench frequency and numerous cryostat rework. Conventionally, a highly stable outer coil is provided to compensate for this.

Returning to FIG. 1, both the refrigerator 17 and the refrigerator turret 18 are normally grounded. At least part of the negative feedback current from the magnet 10 returns to ground via the cryostat body, the refrigerator turret, and the refrigerator. This is known to be disadvantageous in that such currents, typically around a few hundred amperes, cause ohmic heating of the cryostat and refrigerator. Depending on the design of the cryostat, the cryogenic refrigerant container 12 can also be heated by the current flowing through the material of the cryogenic refrigerant container. This causes heating of the cryogenic refrigerant container, resulting in problems such as reduced efficiency of the refrigerator , increased cryogenic refrigerant consumption and possibly magnet quenching.

  The present invention provides the methods and apparatus described in the claims.

  The above and further objects, features and advantages of the present invention will become more apparent from consideration of the following embodiments, given by way of example only, in conjunction with the accompanying drawings, in which:

It is a figure which shows the conventional apparatus which consists of an access turret, refrigerator turret, and electric current lead in the cryostat which accommodates a superconducting magnet. 1 is a perspective view of a turret subassembly according to one embodiment of the present invention. FIG. FIG. 3 is a perspective view of the turret subassembly as shown in FIG. 2 when attached to a cryogenic refrigerant container. FIG. 2 shows a conventional device for a flexible current lead in a fixed current lead cryostat. FIG. 3 shows a flexible current lead device in a fixed current lead cryostat according to one embodiment of the present invention.

Traditionally, the access turret 19 and the refrigerator turret 18 have two cavities in the cryogenic refrigerant container 12 and some complicated welding and assembly operations to assemble each turret into a cryogenic refrigerant container. Two separate entities that you need.

The present invention provides a turret subassembly that houses an access turret, a refrigerator turret, and a means for electrical connection to a magnet. The turret subassembly can be constructed and tested before being assembled as a single unit in a cryogenic refrigerant container. This gives a simple and robust construction procedure that is a feature of the present invention.

By testing the turret subassembly prior to assembly into the cryogenic refrigerant container, the observed defects can be corrected and damage or disposal of the cryogenic refrigerant container in the event of a defect can be avoided. Turret subassembly is leak tested offline before assembly into the cryogenic refrigerant container can reduce the risk of failure of the cryogenic refrigerant container when correction is more difficult and expensive. Many previously difficult assembly tasks, such as welding thin-walled components, are performed during manufacture of the turret subassembly by a relatively simple process that remains to attach the turret subassembly to the cryogenic refrigerant container. Is done.

FIG. 2 illustrates a turret subassembly 24 according to one embodiment of the present invention. One feature of the present invention is a connection box 30 that joins the access turret 32, refrigerator turret 34, and current lead 36 to the turret subassembly for connection to the cryogenic refrigerant container 12. The current lead 36 ensures that the flexible bellows 36a does not carry the aforementioned negative feedback current. Various mounting flanges 38 are provided to hold the various components in their correct relative positions and to provide a mechanical interface for attachment to the cryogenic refrigerant container 12, radiation shield 16, and OVC 14. .

In this way, the connection box 30 functions as a common interface among the access turret 32, the refrigerator turret 34, and the cryogenic refrigerant container 12. FIG. 3 shows an assembly as shown in FIG. 2 assembled in the cryogenic refrigerant container 12. The cover of the connection box 30 is removed, and the inside of the connection box is visible.

Turret subassembly 2 24 shows a refrigerator turret 34 arranged to accommodate the condensing refrigerator for condensation coagulation cryogenic refrigerant vapor in the connection box 30.
This is without affecting the operation of the condensing condenser chiller allows the connection box 30 is partially filled with liquid cryogen during operation. This provides effective local cooling and reduces penetration of hot gas or heat conducted through the access turret 32 and refrigerator turret 34 materials to the cryogenic refrigerant vessel.

Particular advantages of the present invention arise from the arrangement of electrical connections within the connection box 30. Similar to the conventional fixed current lead (FCL) design, the flexible current lead from the magnet must be terminated to the fixed current lead between the access turret 32 and the auxiliary vent 40. As shown in FIG. 2, a portion of the auxiliary vent 40 preferably functions as a positive current lead through the access turret 32. The negative current lead connection can be made through the body of the cryogenic refrigerant container as is conventional.

  According to a preferred feature of the present invention, the flexible current lead is joined to the auxiliary vent 40 and the access turret 32 inside the connection box 30. This can be done by any conventional means such as bolting, soldering, welding, brazing and the like.

Any heat generated by the flexible current leads and the resistance of the electrical connection between the auxiliary vent 40 and the access turret 32 is generated in the connection box 30. This heat is either conducted to the refrigerator or taken up by the cryogenic refrigerant gas escaping via the access turret 32 or the auxiliary vent 40, or evaporation of the liquid cryogenic refrigerant partially filling the connection box 30. Absorbed into the latent heat of Such heat hardly reaches the cryogenic refrigerant container and heats the cryogenic refrigerant gas in the container.

Since the path of the negative current lead is through the cryostat material, the majority of the negative feedback current passes through the refrigerator turret 34 and access turret 32 materials. The close proximity of the negative current lead termination in the connection box 30 and the refrigerator turret 34 minimizes the current through the cryogenic refrigerant vessel, compared to the conventional device as shown in FIG. Reduce the heating effect on the cryogenic refrigerant container. This can be improved by using a relatively thick material for the plate 42 and the connection box 30.

Connection box 30 during operation is preferably partially filled with liquefied cryogen, covering the end of the negative current lead by its thereby as a heat source to the cryogenic refrigerant gas in the cryogen vessel Negative current lead connections can be removed.

The prior art device as shown in FIG. 1 required relatively long flexible current leads 21, 21a to transfer current from the access turret to the magnet. Such a problem is overcome by the present invention because the flexible current lead is usually provided closer to the lower portion of the cryogenic refrigerant container attached to the magnet for access to the current turret 32. The The final position of such a current lead is not regulated in conventional designs, and this current lead can contact the magnet coil, which can reduce the reliability of the magnet system as a whole.

The apparatus of the present invention, the generation of greenhouse gases in the cryogen vessel to minimize significant potential reduction of magnet wire costs through improved condensable margin, namely the cryostat as a reduction and the total required power of the condenser for refrigerators This makes it easy to assemble. The improved thermal environment during ramping may eliminate the need for known high stability outer coils that are conventionally provided to compensate for instabilities caused by heated gas in the cryostat. In other words, this has been determined to allow a cost reduction of about GB £ 1000 (US $ 2000) per magnet assembly at the cost of the superconducting wire for the outer coil.

  Typically, the components shown in FIG. 2 are welded together, such as by TIG welding. Alternative assembly techniques, such as soldering, brazing or adhesive bonding, should be used appropriately with considerable care to ensure proper mechanical strength and electrical and thermal conductivity of each joint Can do.

In accordance with one aspect of the present invention, all welds to thin-walled components such as access turret 32 and refrigerator turret 34 may be performed during construction of the turret subassembly rather than during final assembly of the cryostat as is conventional. . Such thin-wall welding has caused a number of problems so far, often due to the difficulty in accessing the components during assembly into the cryostat and the severe consequences of defective welding on the finished cryogenic refrigerant vessel. It was.

By coupling the access turret 32 and refrigerator turret 34 into a single turret subassembly, the present invention is more at least in that thin-walled components are not required to be welded when assembled into a cryogenic refrigerant container. Enables a robust manufacturing process. Coupling the access turret and refrigerator turret to the turret subassembly provides better access to thin-wall components for welding and assembly operations. This is because the probability of defect welding is reduced and the consequences of such defect welding are not as severe as in the conventional manufacturing process, and only the turret subassembly is reworked without damage to the cryogenic refrigerant vessel. Means good.

The close coupling of the access turret and refrigerator turret has a number of other advantages. As shown in FIGS. 2 and 3, the first stage 44 of the refrigerator turret is linked to a thermal connection 46 to the material of the access turret 32 and a thermal connection 47 to the material of the heat shield. A thermally conductive plate 42 is provided. The plate 42 may be made relatively thick because it typically does not have to be the same structure as the cryogenic refrigerant container wall, as in a case with a similar structure of conventional design. Furthermore, since the access turret 32 and the refrigerator turret 34 are relatively close to each other, effective heat conduction can be provided between the first stage 44 of the refrigerator turret and the access turret. Plate 42 may form part of thermal radiation shield 16 in the completed system. Thereby, the cooling of the access turret 32 is maximized and heat that is transferred from the outer vacuum chamber to the cryogenic refrigerant container during use is removed before reaching the cryogenic refrigerant container. This reduces the heat load on the cryogenic refrigerant vessel below that experienced using conventional access turrets.

As is well known to those skilled in the art, turret components such as access turret 32 and refrigerator turret 34 are paths for heat inflow into the cryogenic refrigerant container. Such turret components are therefore relatively hot components. The use of the turret subassembly 24 of the present invention with the connection box 30 functions to separate the relatively hot turret components from the cryogenic refrigerant container. This eliminates a significant portion of the known problem of heating of the cryogen gas in the cryogen vessel by heat flow through the material of the turret components.
This advantageously allows for a cheaper magnet design since equivalent cooling can be achieved with a less powerful refrigerator. Reduced heating of the cryogenic refrigerant gas in the cryogenic refrigerant container also reduces the likelihood of quenching.
(Final assembly into cryogenic refrigerant container)

An important advantage provided by the present invention resides in an improved assembly method, particularly when joining the turret subassembly 24 comprising the access turret 32 and the refrigerator turret 34 to the cryogenic refrigerant container 12. As shown in FIG. 3, the connection box 30 preferably has sufficient dimensions to cover just one port (hole) 50 in the wall of the cryogenic refrigerant container 12.
Connection box 30 has a hole 52 in one wall 54 that is at least partially aligned with a corresponding port 50 in the wall of cryogenic refrigerant container 12. Connection box 30 is preferably at least substantially open to the opposite side 56 of wall 54 that is aligned with port 50 in the cryogenic refrigerant container. This open side 56 allows easy access to the interior of the connection box 30 and the port 50 in the cryogenic refrigerant container.

As shown in FIG. 3, the turret subassembly is provided in the cryogenic refrigerant container with a hole 52 aligned with the port 50 of the cryogenic refrigerant container 12. The flange 38 can be welded to the OVC to hold the turret subassembly firmly in place. Fixing the flange 38 to the OVC provides external mechanical support for the turret subassembly. A heat shield as shown at 16 may be connected to the refrigerator stage 44 and / or the thermal connection 46 by a thermally conductive braided wire.

If necessary, the extension 40a can be welded to the lower end of the auxiliary vent 40 at this time, or can be attached by other methods. This extension 40a performs an electrical function as described in more detail below. Next, the main body of the connection box 30 is welded to the cryogenic refrigerant container. This may be accomplished by welding around the interior of the hole 52 in the connection box wall 54 if the hole 52 is larger than the port 50 of the cryogenic refrigerant container. Alternatively or additionally, the outer periphery 58 of the connection box 30 can be welded to a cryogenic refrigerant container. Flange 38 and connection box 30 are preferably constructed from thicker materials used for refrigerator turret 34 and access turret 32 so that welding to thin-walled components is not required during this final assembly stage. Is done. To complete the attachment of the connection box, a cover 48 is welded to the open side 56 of the connection box 30 to seal the connection box. The inner volume of the connection box is exposed inside the cryogenic refrigerant container, but is sealed in all other directions. In operation, the connection box effectively forms part of the cryogenic refrigerant container 12.

In this way, final assembly is much simpler than in conventional devices in which the thin access turret 32 and the refrigerator turret 34 are welded separately to the port of the cryogenic refrigerant container by a difficult welding operation. In contrast, the present invention only requires a single welding operation of a relatively thick component that is easily accessible through and / or around the connection box.

  In the final assembly, both the access turret with the auxiliary vent and the refrigerator turret are located towards the side of the cryostat rather than at the top. This allows the overall height of the system to be reduced, simplifying access to the refrigerator and access turret, making maintenance service tasks simpler. As described below, the present invention also provides advantages in the placement and access to the electrical connection with the magnet.

  The advantages provided by the present invention include:

The relatively hot components, such as turrets and electrical connections, are located far from the cryogenic refrigerant container in a path that allows the cryogenic refrigerant gas to escape, thereby reducing heat inflow into the cryogenic refrigerant container.

Close thermal coupling of the access turret and the refrigerator turret improves the cooling of the access turret, reduces the cooling power from the refrigerator needed, have improved reduced margin coagulation by it.

  Flexible lead electrical termination points can be welded or bolted to improve joint reliability, reduce joint resistance, and reduce heat generation in the system .

By placing the flexible current lead termination closer to the bottom of the cryogenic refrigerant container, a reduced length of the unregulated flexible current lead exists in the cryogenic refrigerant container.

By partially filling the connection box, the electrical connection of the flexible current lead to the access turret and the access tube can be contact cooled by the liquid cryogenic refrigerant .

Coupling the access turret and the refrigerator turret reduces the current through the cryogenic refrigerant container.

  Conventionally, the negative grounding point is located on the refrigerator turret 18 and the refrigerator itself is plugged into the refrigerator turret and thereby grounded, so that the current flows through all parts of the OVC, refrigerator and refrigerator turret. Flowing through.

This final assembly process is less risky and more repeatable than existing designs because the turret subassembly is pre-tested and final assembly of the turret subassembly to the cryogenic refrigerant container is a simple welding operation, Requires less time. Contrary to the two ports required in conventional devices with separate refrigerator turrets and access turrets, only one port need be sealed in this cryogenic refrigerant container.

  The relocation of both the access turret and refrigerator turret to the side of the cryostat improves access to these components for easier maintenance service. Such devices also allow for a simpler and smaller appearance cover, improve the aesthetic appearance of the final system, and reduce patient anxiety about the system by making it appear smaller.

(Electrical connection)
With respect to a fixed current lead (FCL) design, there is a requirement to extend the magnet current lead from the magnet to the base of the access turret. The cryostat functions as a negative terminal. Conventionally, the flexible current leads 21, 21 a extend from the base of the magnet and are bolted to the base of the vent pipe 20 and the auxiliary vent 40 as shown in FIG. 4, for example.

  FIG. 4 shows a conventional device for connecting a current lead to a superconducting magnet in a cryostat. Conventionally, at least a portion of the auxiliary vent 40 functions as a positive current lead through the access turret 19 and vent tube 20. The flexible positive current lead 21 is typically bolted or soldered to the base of the auxiliary vent 40. The flexible negative current lead 21a is typically bolted or soldered to the base of the vent tube 20.

The disadvantage of the conventional flexible lead termination device shown in FIG. 4 is that the contact resistance of the bolted or soldered joint causes Joule heating and heat dissipation at the base of the vent tube 20 during ramping. It is to raise the temperature of the cryogenic refrigerant gas by conduction and convection in the cryogenic refrigerant container 12. The flexible current leads 21, 21a conduct the relatively high temperature of the vent tube 20 (up to 90K at its base in the case of a helium system) to the cryogenic refrigerant container. These effects can ultimately cause quenching. Conventionally, a highly stable outer coil is required to compensate for this.

One aspect of the present invention is to provide auxiliary vent 40 and current to minimize heat input to the cryogenic refrigerant vessel during ramping, reduce the possibility of quenching during operation, and reduce the risk of assembly errors. An apparatus for combining the functions of leads 62 and 64 is provided.

One embodiment of the present invention illustrating this aspect is shown schematically in FIG. The positive flexible current lead 62 from the magnet is electrically conductive to the end of the auxiliary vent extension 40a, which is preferably made of high-purity metal and can be a copper tube when the magnet is assembled in the cryogenic refrigerant container 12. In particular, it is soldered, bolted, brazed, or otherwise attached. This auxiliary vent extension 40a is later electrically conductively welded and soldered to the auxiliary vent 40 of the turret subassembly of the present invention when the turret subassembly is provided in the cryogenic refrigerant container at the final stage of construction. It is bolted, brazed or otherwise attached (40b). The conductive joint 40 b connects the auxiliary vent extension 40 a to the auxiliary vent 40, so that the auxiliary vent extension 40 a is integrated with the auxiliary vent 40. In the illustrated embodiment, unlike the auxiliary vent 40 itself disposed within the access turret 32, the auxiliary vent extension 40 a extends into the cryogenic refrigerant container 12. The large surface area and high purity of the material of the auxiliary vent extension 40a is combined to minimize its electrical resistance and thus also minimize the generation of heat in the cryogenic refrigerant container during current ramping. The contact resistance is less likely to change than that of existing designs because the connection between the flexible lead 62 and the auxiliary vent extension 40a can be made with sufficient access to the necessary components. The inventors have shown that this device reduces the cryogenic refrigerant gas temperature in the cryogenic refrigerant container, allowing a cheaper and / or more stable magnet design solution.

In further contrast to conventional devices, the negative current lead connection point 66 has been moved away from the interior of the cryogenic refrigerant container 12. Rather, the negative current lead connection point 66 is exposed to the flow of cryogenic refrigerant gas above the access turret 32 and auxiliary vent 40. The negative current lead 64 can be connected to the access turret 32 as shown in FIG. 5 or can be attached to the wall of the connection box 30. The cryogenic refrigerant gas flow carries any heat generated by the current flowing through the resistive negative lead termination 66 away from the cryogenic refrigerant container 12 during ramping. Any heated cryogenic refrigerant gas is released via the access turret 32 or auxiliary vent 40 and does not enter the cryogenic refrigerant container 12. Furthermore, the wall of the connection box 30 can be made significantly thicker than the wall of the cryogenic refrigerant container, since the connection box is relatively small and easily manufactured from a flat panel. Thus, a larger material cross section is available to carry the current, which prevents resistance heating of the cryogenic refrigerant container and reduces the amount of heat generated during ramping.

  The turret subassembly 24 having the connection box 30 configuration of the present invention can be used to weld a joint 40b that joins the auxiliary vent extension 40a to the auxiliary vent 40 or the like once the turret subassembly 24 is attached to the cryostat. And the bolting of the negative current lead at the associated connection point 66. The contact resistance for both positive and negative current leads is less likely to change than conventional solder designs.

Cryogenic refrigerant gas escaping from the cryogen vessel 12, through the auxiliary vent 40 and its extension 40a, also through the around these, is generated by the current flowing through the auxiliary vent and its extension any Even with heat, this heat is efficiently cooled and removed.

Negative lead connection point In an alternative arrangement, either provided on the boundary surface of the magnet formed body and the inner surface of the cryogen vessel, or given a short flexible current leads to the inner surface of the cryogen vessel. In a solenoid type device where the cryogenic refrigerant container is hollow cylindrical, the negative current lead connection point may be provided on the inner surface of the cryogenic refrigerant container lumen. Such an embodiment is advantageous in that current flows through the cryogenic refrigerant container material and the cryostat without direct heating of the cryogenic refrigerant gas. The negative current lead connection point can be arranged to be cooled by direct contact with the liquid cryogenic refrigerant . Such an improvement in the thermal environment of the coil during ramping becomes increasingly important when a minimal cryogenic refrigerant inventory system is considered. A secondary effect of such a device is that if the space at the turret / cryogenic refrigerant container interface is marginal, the assembly of the access turret is not necessary because a negative current lead connection need not be established in this position. Is simplified. Such a connection device can be used independently of the positive connection device using the auxiliary vent described above and independent of the turret subassembly of the present invention.

This aspect of the present invention thus provides a novel device for auxiliary vent and current lead assembly in a fixed current lead access turret device. This novel device minimizes the generation of warm gases in the cryogenic refrigerant container and combines the function of each component to reduce cost and complexity. A simpler manufacturing process is possible.

  The present invention allows for a low cost fixed current lead (FCL) turret design and, similarly, a less expensive magnet that is more predictable in performance and less likely to require rework during manufacture. Enables the design of

  Although the invention has been described with particular reference to certain embodiments, many variations of the described embodiments are possible and are within the scope of the invention as claimed. It is clear to the contractor.

Although specific references have been made to helium cryogenic refrigerants , it will be apparent that any suitable cryogenic refrigerant may be used. References to “positive” and “negative” current leads, terminations, etc. are used as labels for convenience only, reflecting common practice in the art. Of course, the connection of the positive and negative current leads can be reversed without departing from the scope of the present invention. If necessary, alternating voltages and currents can be applied to the described current leads, terminations, etc. without departing from the scope of the present invention.

Claims (24)

A subassembly for use as part of a cryostat,
An access turret (32) containing an auxiliary vent (40);
A refrigerator turret (34) for housing the refrigerator;
A connection box (30) for connecting the access turret and the refrigerator turret, the connection box (30) having an opening (52) in one wall (54) constituting the connection box;
Means (38) for attachment of said subassembly to a cryogenic refrigerant container (12). The condensation surface for condensing a cryogenic refrigerant vapor arranged to be cooled by a refrigerator accommodated in the refrigerator turret (34) is exposed inside the connection box. Subassembly. The subassembly of claim 2 in which the liquid cryogen which is reduced coagulation in use are arranged inside the junction box so as to at least partially fill. When mounted in front Symbol cryogen vessel, the access turret and the refrigerator any one of claims 1 to 3, top portion is arranged to extend far no higher than the top of the cryostat of the turret Subassembly as described in. The refrigerator turret is attached and the condensing surface and the first heat stage (44) is thermally to the first heat stage (44) heat stage attached to the access turret (46) The subassembly according to any one of claims 1 to 4, which is connected.   A subassembly according to any one of the preceding claims, wherein the connection box comprises a removable wall portion (48) opposite the opening (52).   A subassembly according to any one of the preceding claims, further comprising means for connection of electrical leads within the connection box.   The means for connecting comprises means for connecting a first electrical lead to the auxiliary vent in the connection box; means for connecting a second electrical lead to the material of the connection box The subassembly of claim 7 comprising: A cryostat comprising a cryogenic refrigerant container equipped with the subassembly according to any one of claims 1 to 8. A cryostat comprising a cryogenic refrigerant container equipped with the subassembly according to claim 7 or claim 8,
The cryogen container, torque cryostat to accommodate the cooled electrical device electrically connected to said means for connecting. (A) assembling the subassembly according to any one of claims 1 to 8;
(B) and assembling the cryogen vessel equipped with a port (50) in the wall of the cryogen container;
(C) The port is sealed by the arrangement of the connection box, and the inside of the connection box is exposed to the inside of the cryogenic refrigerant container by the opening (52) and the port (50). A method of assembling a cryostat comprising the steps of: attaching the subassembly to the cryogenic refrigerant container by attachment means.   The method of assembling a cryostat according to claim 11, further comprising testing the subassembly for manufacturing defects between steps (a) and (c). The cryogenic refrigerant container is electrically connected to means for connection of electrical leads in the connection box by electrical leads passing through an opening formed by the port (50) and the opening (52). 13. A method of assembling a cryostat according to claim 11 or claim 12, wherein the cooled electrical device is accommodated. The connection box comprises a wall portion (48) removable on the side opposite to the opening (52), said removable wall portion, said to the cryogen container in order to seal the connection box Following assembly of the subassemblies, said wall portion which has been removed is found standing on the set is in the connection box, a method of assembling a cryostat according to any one of claims 11 to 13. The cryogenic refrigerant container (12) contains the cooled electrical device, the subassembly contains a conductor, and the method comprises:
Electrically and mechanically connecting a first flexible current lead (62) from the cooled electrical device to an extension (40a) prior to assembly of the cryogenic refrigerant container;
Wherein the assembling cryogen container having the ports around the cooled electrical device (50) (12);
Said extension having an attached flexible current lead, and letting through to the outside of the cryogen vessel through the pre Kipo over preparative;
12. The method of claim 11, further comprising: electromechanically connecting the conductor to the extension (40b) to provide an electrical conduction path through the access turret to the cooled electrical device. The method of assembling the cryostat as described in any one of -14. 16. The method of claim 15, wherein the method further comprises allowing in use cryogenic refrigerant gas to flow out of the cryogenic refrigerant vessel via the access turret to cool the electrical conduction path. When the extension portion and the conductor are mechanically connected, to claim 16 which is arranged to function as an auxiliary vent (40) for conveying the cryogen gas from the cryogen vessel The method described.   The method of any one of claims 15 to 17, further comprising connecting a second flexible current lead (64) to an inner surface (66) of the access turret (32).   18. A method according to any one of claims 15 to 17, wherein the access turret (32) forms part of a subassembly according to any one of claims 1-8. Said cryogen vessel (12) has the port (50);
A first flexible current lead (62) electrically and mechanically connects the cooled electrical device to the extension (40a);
The subassembly comprises the access turret (32) for accommodating a conductor (40) attached to the cryogenic refrigerant container on the port (50);
A cryostat according to claim 10, wherein the conductor (40) is electromechanically attached to the extension (40b) to provide an electrical conduction path through the access turret to the cooled electrical device. 21. The cooled electrical device of claim 20, wherein the access turret is configured to provide an escape path for cryogenic refrigerant gas to flow out of the cryogenic refrigerant container thereby cooling the electrical conduction path. A cryostat to house. Said conductor and said extended portion that is mechanically connected was placed to serve as the auxiliary vent for transporting cryogenic refrigerant gas from the cryogen vessel, according to claim 20 or claim 21 A cryostat that houses the electrical equipment.   23. A cryostat housing an electrical device according to any one of claims 20-22, further comprising a second flexible current lead (64) connected to an inner surface (66) of the access turret (32). 24. A cryostat housing a cooled electrical device according to any one of claims 20 to 23, further comprising a second flexible current lead (64) connected to the inner surface (66) of the cryogenic refrigerant container.

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